Hexagram antenna

ABSTRACT

Two triangular radiating elements are interlaced in a helical winding about a common axis to form a single antenna structure. The elements are wound in opposite directions and are laterally separated, thus reducing the RF coupling between them and improving the circularity of each radiating pattern with one radiating element wound in one direction and the other in the opposite direction, a dual circularity is achieved from the same physical volume.

I United States Patent l 13,569,977

[72] inventor William B. Koller [56] References cu d 9:3 lohio UNITEDSTATES PATENTS [2!] A pl. No. i 2 616 046 10/1952 Marston et al 343/895X22 Filed Dec. 26, 1968 Patented Mar. 9, 1971 3,083,364 3/1963 .Scheldorf343/843 [73] Assignee Goodyear Aerospace Corporation Primary ExammerEhLieberman Akron, Ohio Assistant ExaminerMarvin Nussbaum Attorney-J. G.Pere [54] flExfscRAM ANTENNA ABSTRACT: Two triangular radiating elementsare interlaced 7 Chum 4 Drawmg Figs in a helical winding about a commonaxis to form a single an- [52] U.S. Cl. 343/848, tenna structure. Theelements are wound in opposite 343/895 directions and are laterallyseparated, thus reducing the RP [51] Int. (I H0lq l/36, coupling betweenthem and improving the circularity of each HOlq l/48 radiating patternwith one radiating element wound in one [50] Field of Search 343/874,direction and the other in the opposite direction, a dual circu- 895,843, 848 iarity is achieved from the same physical volume.

PATENTED m 9197:

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FIG.-2

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ATTORNEYS HEXAGltAli/l ANTENNA ll-lleretofore the use of helicalantennas has been well known, with these antennas designed to provide apredetermined directional radiating and reception pattern. Variousmethods have been utilized'to achieve circularity in the patterns, andto prevent mutual RF coupling between separate radiating elements ifmore than one element is utilized. However, the problem of preventingmutual RP coupling, and obtaining dual circularity in one compositeantenna structure is needed by the art.

Therefore, it is the general object of the invention to meet the needsof the art by providing dual circularity in radiating and receptionpatterns on a single radiating structure, and where mutual couplingbetween separate radiating elements is substantially reduced.

For a better understanding of the invention reference should be had tothe accompanying drawings wherein:

FIG. 1 is a side elevational view of an antenna made according to oneembodiment of the invention;

FIG. 2 is a cross-sectional plan view of the antenna of FIG. ll taken online 2-2 thereof;

FIG. 3 is an enlarged broken away side view of the base of the antennaof FIG. 1 showing how the feed is provided to the separate radiatingelements;

FIG. 4 is a cross-sectional plan viewof a second embodiment of theantenna of the present invention.

With reference to the embodiment of the invention shown in MG. l of thedrawings, the numeral indicates generally an elongated supporting posthaving an axis which is carried by a mounting base 112 in anyconventional manner so the axis is substantially normal to the surfaceof the base 12. The post is preferably hexagonal in cross section asseen in FIG. 2. The invention comprises a pair of radiating elements Mand 16 which are wound in an interrelated triangular helix up the lengthof the support post 10, and concentric with the axis thereof with equaland uniform longitudinal spacing between the windings, as illustrated.The triangular shape will fit around the hexagonal post 10 as shown inlFlG. 2. Preferably, the triangles are equilateral, although this is notabsolutely necessary. The elements 114 and I6 will normally be copperwire, but any suitable element to provide electromagnetic radiation willmeet the objects of the invention. It should be understood that the post10 is purely for purposes of support, and that any low loss material forsupporting the antenna would be used. Also, of course, if the wiresthemselves have sufficient strength, or if the antenna is to be used ina space environment the post 10 may not be necessary. The onlyrequirement is that the antenna windings be concentric to some commonaxis.

The antenna of FIG. 1 was made as an experimental model. The pitch angleof the triangular helices was equal to 19.5 with a design bandwidth ofbetween 1.00 to 2.00 Ghlz. The ground plane diameter established by base12 was 10 inches. The base l2 was made from a conductive materialwhereas the post id was made from a dielectric material. However, it isto be understood that the pitch angle and bandwidth would changedepending upon the specific requirements of the antenna.

The pitch angle of the antenna elements could be continually decreasingalong the structure with a similar decrease in the dimension of thetriangles to form a pyramidal like antenna. A structure of this typewould have a broader frequency bandwidth.

The unique aspect of this antenna and that critical to its properoperation is that the triangular helices are wound in opposite directionabout a common axis llla, as is best illustrated in FIG. 2;.Essentially, winding 14 is in a right-hand pattern while winding i6 isin a left-hand pattern. The winding 14 is thus capable of transmittingand receiving right-hand circularly polarized radiation, with thewinding 16 capable of transmitting and receiving left-hand circularlypolarized radiation.

With the exception of the feed line lengths at the base of theinterlacing of the two helices requires that one of them be displacedsome predetermined pitch distance higher off the ground plane. Thisdistance to achieve minimum RF coupling can be determined eitherexperimentally or mathematically. The opposite directing of the windingsin the triangular helix pattern provides the greatest actual spacedrelationship between the wires so as to substantially reduce mutualcoupling. Specifically, as is quite clearly shown in H6. 2, thetriangnilar points of each winding M'and 16 are at considerable spaceddistances from the flat bases adjacent thereto, thus providing themaximum spaced relationship possible which greatly reduces mutualcoupling.

FIG. 3 illustrates the base feed wires designated 14a and 160,respectively, and shows the vertical displacement in the right-handcircular polarization feed on line Ida to provide the predeterminedpitch distance displacement. The lines are actually fed from a coaxial,cable 20 with the shield of the cable electrically connected to theground plane. The purpose of coordinating displacement and pitch angleis to hold VSWR to the lowest possible value at the junction between thecoaxial cable 20 and the antennas.

The radiation pattern and reception pattern with respect to each of thewindings l4 and 16 is a uniformly directed lobe which has much greaterpredictability than normal countrawound helical antennas because of thelack of mutual coupling between windings. Also, it should be understoodthat while one winding can be operating on the right-hand circularlypolarized pattern, the other winding could be receiving left-handcircularly polarized signals, thus making the antenna extremelydesirable for use with earth orbiting satellites, for example, where oneground station would radiate right-hand circularly polarized waves to bedetected by the right-hand circularly polarized antenna on thesatellite, to trigger a lefthand circularly polarized signal from thesatellite to be received at the left-hand circularly polarized antennaon the earth. This can be achieved in compact relationship on the singleantenna structure.

FIG. 4 illustrates a modified embodiment of the invention utilizingsubstantially a square pattern in the windings in lieu of the triangularpattern. Again the points or corners are alternately positioned toprovide the greatest possible spacing to prevent mutual coupling. It isbelieved that a figure with any more sides than four would not meet theobjects of the invention.

It should be understood that the angular relation of the radiatingelements to the ground plane could vary according to the particularradiation requirements of the antenna, but that the antenna should havea ground plane, and some helical configuration to the triangularwindings. The antenna is an intermediate frequency bandwidth antennatransmitting and receiving with different sense polarizations atslightly different frequencies, and is quite effective for thesepurposes. The mutual coupling between antennas'is greatly reducedbecause of the hexagram configuration of the antenna. Proper phasing ofthe radiating elements 14 and to, both in space and time will providethe best operating characteristics for each construction, determined fora particular required condition.

While in accordance with the patent statutes, only one best knownembodiment of the invention has been illustrated and described indetail, it is to be understood that the invention is not limited theretoor thereby, but that the inventive scope is defined in the appendedclaims.

I claim:

ll. An antenna which comprises:

at least two radiating elements wound in a geometric pattern of not morethan four sides in opposed helixes along a common axis with a uniformlongitudinal spacing between elements and alternate positioning ofangular changes in the elements whereby maximum spacing between elementsis achieved to reduce mutual coupling; and

means to form a ground plane on one end of the elements.

2. An antenna according to claim 1 which includes a connector forfeeding the elements, where said means to form a ground plane is a baseand where the connector is electrically connected to the base wherebythe base provides a ground plane for the antenna.

3. An antenna according to claim 2 which includes a post to support theradiating elements, which post in cross section has the shape of ahexagon, and the shape of the elements in plan is an equilateraltriangle closely fitting around the longitudinal axis of the post.

4. An antenna according to claim 3 where the longitudinal displacementbetween elements is predetermined as a portion of the pitch distance forone convolution of the helical wrap of each element to achieve minimumVSWR between the connector and the radiating elements.

5. An antenna according to claim 4 where the pitch angle of the elementsis 195 and where each element has a designed bandwidth between 1.00 to2.00 Gl-lz.

6. An antenna which comprises: a base to provide a ground plane; and apair of elements capable of transmitting and receiving electromagneticradiation mounted to the base and extending substantially normal theretoin concentric relation to an axis substantially perpendicular to thesurface of the base which is characterized by the elements being woundin opposed triangularly shaped helical convolutions about the axis witha uniform longitudinal spacing between elements whereby each apex isassociated with a corresponding base of the adjacent element to reducemutual coupling therebetween upon energization.

7. An antenna which comprises:

at least two radiating elements wound in a geometric pattern of not morethan four sides in opposed helixes along a common axis with uniformlydecreasing longitudinal spacing between elements, with a similar uniformdecrease in the size of the convolutions of each helical wrap, and withalternate positioning of angular changes in the elements whereby maximumspacing between elements is achieved to reduce material coupling; and

means to form a ground plane on one end of the elements.

1. An antenna which comprises: at least two radiating elements wound ina geometric pattern of not more than four sides in opposed helixes alonga common axis with a uniform longitudinal spacing between elements andalternate positioning of angular changes in the elements whereby maximumspacing between elements is achieved to reduce mutual coupling; andmeans to form a ground plane on one end of the elements.
 2. An antennaaccording to claim 1 which includes a connector for feeding theelements, where said means to form a ground plane is a base and wherethe connector is electrically connected to the base whereby the baseprovides a ground plane for the antenna.
 3. An antenna according toclaim 2 which includes a post to support the radiating elements, whichpost in cross section has the shape of a hexagon, and the shape of theelements in plan is an equilateral triangle closely fitting around thelongitudinal axis of the post.
 4. An antenna according to claim 3 wherethe longitudinal displacement between elements is predetermined as aportion of the pitch distance for one convolution of the helical wrap ofeach element to achieve minimum VSWR between the connector and theradiating elements.
 5. An antenna according to claim 4 where the pitchangle of the elements is 19.5* and where each element has a designedbandwidth between 1.00 to 2.00 GHz.
 6. An antenna which comprises: abase to provide a ground plane; and a pair of elements capable oftransmitting and receiving electromagnetic radiation mounted to the baseand extending substantially normal thereto in concentric relation to anaxis substantially perpendicular to the surface of the base which ischaracterized by the elements being wound in opposed triangularly shapedhelical convolutions about the axis with a uniform longitudinal spacingbetween elements whereby each apex is associated with a correspondingbase of the adjacent element to reduce mutual coupling therebetween uponenergization.
 7. An antenna which comprises: at least two radiatingelements wound in a geometric pattern of not more than four sides inopposed helixes along a common axis with uniformly decreasinglongitudinal spacing between elements, with a similar uniform decreasein the size of the convolutions of each helical wrap, and with alternatepositioning of angular changes in the elements whereby maximum spacingbetween elements is achieved to reduce material coupling; and means toform a ground plane on one end of the elements.